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I've read this excellent question about how to deal with several disks of different sizes. Parasietje's accepted answer was great.

Two or three related questions :

  1. Let's say I have three disks : 40 GB, 80 GB, 320 GB. What is the best strategy to maximize disk space availability (and ensure safety) ? We could agregate 80+40=120 and replicate this virtual device to the big disk, there is 200 GB lost here. Is there a better refinement ? How to do this calculation with the ZFS strategy Parasietje talks about ?
  2. Let's say that I plan to add later a couple of 80 GB disks to the cluster, and don't want to reinstall the whole thing. Is there a better strategy than use them to expand the virtual device ?
  3. Let's say now that I want to tolerate two faulty drives with this new harware (1x40, 3x80, 1x320). I guess that the smaller is useless and I should do a RAID-6 on the remaning drives, giving me 160 GB of available space. Any better idea ?
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Samuel
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1 Answers1

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https://en.wikipedia.org/wiki/Logical_Volume_Manager_(Linux)

LVM is used for the following purposes: Creating single logical volumes of multiple physical volumes or entire hard disks (somewhat similar to RAID 0, but more similar to JBOD ), allowing for dynamic volume resizing. Managing large hard disk farms by allowing disks to be added and replaced without downtime or service disruption, in combination with hot swapping . On small systems (like a desktop), instead of having to estimate at installation time how big a partition might need to be, LVM allows filesystems to be easily resized as needed. Performing consistent backups by taking snapshots of the logical volumes. LVM can be considered as a thin software layer on top of the hard disks and partitions, which creates an abstraction of continuity and ease-of-use for managing hard drive replacement, repartitioning and backup.

user657451
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